The fatal shooting of two men in their twenties is the latest incident in suburban feuds between criminal gangs fighting over territory, police in Stockholm said.

The men were shot dead late on Wednesday while sitting in a car in a residential area of Kista, north-west of the Swedish capital.

In 2017 alone there have been 17 shooting episodes in Stockholm, with seven dead - including five this week - and 14 injured, local police chief Ulf Johansson said.

Attacks have included the use of Kalashnikov-style rifles and hand grenades, he added.

"These are young men with access to weapons," Mr Johansson said, adding there are up to 12 conflicts in the Stockholm area between criminal gangs over drug markets and territory.

"This is of course alarming and very serious," he told a news conference.

Mr Johansson said police in the Swedish capital had asked for extra resources but did not give details.

No suspects have been arrested after the overnight shooting and the motive was not known.

Swedish broadcaster SVT and the Expressen tabloid said one of those killed late on Wednesday was a leading member of the Lion group, which it described as well known for its drug-linked criminal activities.

SVT said the Lions were in conflict with the Wolfpack Brotherhood and the shooting may be linked to that.

Police declined to comment on the ongoing investigation.

Swedish media said the victims were shot in the head several times, adding investigators would look at previous incidents in the area.

On Monday, two people were stabbed to death in another nearby Stockholm suburb.

It was unclear if the cases were linked.